The invention relates to a disc brake system for a motor vehicle, having a brake mechanism with a reduced size.
A disc brake system for a motor vehicle is well known from prior art. Such a disc brake system usually comprises:                a brake disc, rotary movable around a disc axis, intended to be rotary connected with a wheel of the motor vehicle, and        a brake mechanism, comprising:                    at least one brake pad, movable in a first direction parallel to the disc axis, between a first position away from the brake disc, and a second position in contact with the brake disc,            a cylinder, in particular a pneumatic cylinder, having a rod movable in a second direction, parallel to the first direction,            a lever, rotating around a lever axis, the lever being connected to said piston so as to be driven in rotation around the lever axis when the piston is moved,            a cam element, arranged to convert a rotary motion of the lever around the lever axis, into a translation motion in the first direction,            a piston, expanding between a first end connected to the brake pad and a second end connected to the cam element, so as to transmit a translation motion in the first direction from the cam element to the brake pad, and            a housing, at least for the lever, the cam element and the rod. Usually, an adjuster, for compensating a reduction in the thickness of the brake pad in the first direction, is also housed in the housing. Thus, the housing is intended to protect this adjuster, the lever, the cam element and the piston against aggressive particles that would imply corrosion, such as water and/or dust.                        
The brake pad is intended to be pushed by the piston against the brake disc, so as to apply a braking friction against this brake disc.
To this end, the rod is actuated, so as to push the lever, so that said lever is driven in a rotary motion around the lever axis. The cam element is then moved by the lever in motion, so as to convert the rotary motion of the lever into a translation motion of the piston. Thus, the piston is pushed towards the brake disc, pushing the brake pad against this brake disc.
The brake mechanism generally also comprises at least one resilient element intended to resiliency return the brake pad away from the brake disc when no pushing force is applied by the piston on this brake pad, i.e. when the piston is not actuated.
In such a brake mechanism, the lever axis is perpendicular to a plane comprising the disc axis and the axis of the piston. In other words, when the brake mechanism is mounted vertically above the brake disc, the lever expands in a vertical direction, and the lever axis expands in a horizontal direction.
It should be noticed that the lever needs a sufficient space for allowing a rotary motion of this lever along its stroke. To this end, the housing generally comprises a boss or a specific volume delimiting this space, this boss or specific volume extends radially and outwardly away from the disc axis, i.e. towards the rim of the wheel.
This boss or specific volume is usually in a conflict with the rim of the wheel. As a consequence, the housing has to be deported in a direction parallel to the disc axis, to avoid such a conflict. So, the brake mechanism has to be overdimensioned so as to compensate this deportation. Thus, the size of the brake mechanism is relatively large.
It is desirable to overcome this drawback, by proposing a brake mechanism that is more compact than a previously disclosed brake mechanism from prior art.
To this end, an aspect of the invention relates to a disc brake system for a wheel of a motor vehicle, comprising:                a brake disc, rotary movable around a disc axis, intended to be rotary connected with said wheel, and        a brake mechanism, comprising:                    at least one brake pad having a central pad axis that is parallel to the disc axis and that defines a first direction according to which the brake pad can move between a first position away from the brake disc, and a second position in contact with the brake disc,            a cylinder, in particular a pneumatic cylinder, having a rod movable in a second direction,            a lever, rotatory movable around a lever axis, the lever having a lever end that is connected to said rod such that the lever is driven in a rotary motion around the lever axis when the rod is moved in the second direction,            a cam element, arranged to convert the rotary motion of the lever around the lever axis, into a translation motion in the first direction,            at least one piston, expanding between a first end connected to the brake pad and a second end connected to the cam element, so as to transmit a translation motion in the first direction from the cam element to the brake pad, and            a housing, at least for the lever, the cam element and the piston, characterized in that, considering a plane comprising the disc axis and the first the central pad axis, the lever axis is inclined relative to said plane, at an angle different from 90°.                        
Throughout this patent application, the term “central pad axis” refers to the axis of the brake pad that is parallel to the disc axis and that is passing through the centre of gravity of the brake pad. When the brake mechanism comprises only one piston, the central pad axis is preferably merged with the main axis of the piston.
By inclining the lever axis at an angle different from 90° relative to said plane, the lever stroke is lowered in a radial direction from the disc axis, so that the boss or the specific volume in the part of the housing that is furthest from the disc axis can be reduced. Thus, the housing of the invention can be made more compact than a housing from prior art, so that this housing can be arranged in a whole or almost in a whole inside the rim of the wheel. Thus, this housing allows more free space for other components that are disposed around the brake system, such as suspension, wheel axles, chassis, etc.
It should be noticed that the invention reduce the size of the brake mechanism, without changing the moment arm of the lever.
The term “part of the housing that is furthest from the disc axis” refers to the part of the housing that is radially furthest from the disc axis and therefore that is radially closest to the rim of the wheel.
A brake mechanism according to the invention can further comprise one or several of the following features, alone or in combination:                The lever axis is inclined relative to the plane, at an angle between −35 and 55°.        The lever axis is preferably inclined relative to the plane at an angle between 10 and 55° such that the end of the lever that is confected by said rod is located in the half part of the housing that is furthest from the disc axis. To be more precise “the half part of the housing that is furthest from the disc axis” refers to the inside part of the housing that extends between the wall of the housing that is furthest from the disc axis and a median line that extends between the wall of the housing that is furthest from the disc axis and the wall of the housing that is closest to the disc axis.        The lever axis is inclined relative to the plane (P) at an angle of 30°.        The lever expands in a direction that is perpendicular to the lever axis.        The lever is inclined between 0 and 45° with respect to a direction that is perpendicular to the lever axis.        Said plane is vertical when the brake mechanism is mounted on a disc brake system.        The cam element is a cylinder having an outer surface comprising at least a rounded part around a cam axis, said cam axis is parallel to the lever axis and it is different from this lever axis, the cam element is rotary movable around the lever axis, and the second end of the piston is arranged in contact with the rounded part of the cam element.        The lever is integral with the cam element.        The disc brake system also comprises an adjuster, for compensating a reduction in the thickness of the brake pad in the first direction, said adjuster being housed in said housing.        
These and other aspects and advantages will become apparent upon reading the following description in view of the drawing attached hereto representing, as non-limiting examples, embodiments of a vehicle according to the invention.